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Forests and Woodlands of the Sky Islands: Stand Characteristics and Silvicultural Prescri ptions

2 3 Gerald J. GoHfried1, Peter F. Ffolliott , and Leonard F. DeBano

Abstract.-The mountains of the Sky Islands or Madrean Archipelago are noted for their biological diversity. The higher elevations support pine, mixed conifer, and spruce-fir forests, while encinal and pinyon-juniper woodlands are found at more intermediate elevations. The highest forest zones are representative of the Rocky Mountain flora and the woodlands are representative of the Madrean flora of Mexico. Local and regional climatic patterns over the past 24,000 years have influenced the establishment and survival of these ecosystems. Past natural and human disturbances have affected stand conditions. The diversity of forest and woodlands can be observed on the five highest and largest mountain ranges in southeastern Arizona, namely, the Santa Catalina, Santa Rita, Huachuca, Chiricahua, and Pinaleno Mountains. Human activities in the forests and woodlands have changed over time. Some traditional industries have declined while demands for other activities, such as recreation, have increased. There are concerns about the condition of these mountain ecosystems. Silviculture can be used as a ecosystem management tool to enhance long-term productivity of a varietY of resources and amenities, to enhance biological diversity, and to help ensure forest and woodland health.

INTRODUCTION drean flora of Mexico. Some species find their northern or southern limits in these mountains. The mountains of the Madrean Archipelago, The mountains have allowed for the migration of or Sky Islands of southern Arizona, New Mexico, some species to the north or south (Gehlbach and northern Mexico are recognized for their di­ 1981). The northern mountain ranges in the Ma­ verse mixtures of plants and animals. Variety drean Archipelago of Arizona have more characterizes the region, which includes an area components of the Rocky Mountain flora and approximately 160 to 175 km on each side of the fauna than those further south, where Mexican af­ international border (Gehlbach 1981). The highest finities are greater. Local and regional climatic mountains support pine, mixed conifer, and patterns and the natural impacts of fire, wind, and spruce-fir forests, while encinal and pinyon-juni­ insects have influenced the establishment and sur­ per woodlands are common at more intermediate vival of the forests and woodlands. elevations. The varied plant communities and lfuman activities since pre-historic times have their animal populations reflect the meeting, mer­ affected the distribution, characteristics, and gence, and coexistence of species representative of health of the region's forests and woodlands. Al­ the northern Rocky Mountain flora or the Ma- though these lands have been heavily utilized, especially since European settlement, 96 percent of the original postglacial forests and woodlands 1Gerald J. Gottfried is Research Forester, USDA Forest Service, still exist (Gehlbach 1981). Utilization of these Rocky Mountain Forest and Range Experiment Station, Flagstaff, AZ. lands continues to change; traditional land uses to 2Peter F. Ffol/iott is Professor, School of Renewable Natural Re­ supply wood for forest products or mining indus­ sources, University of Arizona, Tucson, AZ. tries or forage for livestock grazing are often 3Leonard F. DeBano is Supervisory Soil Scientis~ USDA Forest Serv­ ice, Rocky Mountain Forest and Range Experiment Station, Tucson, AZ. percE~ived to be in conflict with increasing de-

152 mands for recreation, landscape preservation, wa­ for example, the Chiricahua Mountains are ap­ tershed protection, and habitats and site proximately 64 km long and between 6 and 32 km requirements of rare species. Demands for fuel­ wide (Jackson 1970). wood have increased. Privately owned woodlands are increasingly being converted to home sites, causing land management conflicts, Climate fragmentation of wildlife habitats, and potential fire control problems. There are concerns about The regional climate in southeastern Arizona the sustainability and health of the mountain eco­ is semiarid, and precipitation is bimodal. Winter systems under pressure from human activities precipitation is associated with frontal storms and natural effects of fires and insect infestations, originating in the Pacific Ocean that move west­ and the impacts of past fire suppression activities. erly over the State. Winter conditions generally Silvicultural prescriptions can be developed to prevail from October through May, but most in­ help ensure long-term sustainability and to pro­ tense storms occur between mid-November and vide for forest and woodland health. Silviculture mid-April. Late spring and early summer are typi­ can be used as an ecosystem management tool to cally dry. Summer monsoon moisture begins to enhance wildlife habitat, the production of herba­ enter the region in late June or July; storms are ceous species for both livestock and wildlife, and convective resulting from the flow of tropical air watershed protection. It can also be used to en­ over heated mountain terrain. Intense summer hance and maintain biological diversity within the thunderstorms, which are common over moun­ region. tains, result from a combination of thermal The objectives of the paper are to review the heating, orographic uplifting, and conveyance of characteristics of the forests and woodlands of the air on the windward side of the mountains Madrean Archipelago, some of their historical (Gottfried 1989). Late summer and early autumn land uses, and some appropriate silvicultural pre­ tend to be dry, although tropical cyclones during scriptions. Riparian woodlands, an extremely this season may push moisture into the State pro­ important ecosystem within the Sky Islands, will ducing record rainfalls. Summer precipitation not be covered here; they are covered elsewhere in may account for up to 70 percent of the annual these proceedings. Although the region contains total in southeastern parts of Arizona (Bahre numerous isolated mountain ranges that vary in 1991). Records at the Chiricahua National Monu­ physical size and vegetational associa!ions, the ment indicate that 50 percent of the precipitation current effort will concentrate on the five largest occurs in July and August, and that May is the and highest mountain ranges: Santa Catalina, driest month. Annual precipitation ranges from Huachuca, Santa Rita, Chiricahua, and the Pi­ 230 to 635 mm, although higher elevations can re­ naleno or Graham Mountains. ceive over 890 mm, often as snows in December and January. Bahre (1991) indicated that average temperatures at higher elevations can average 1.60 GENERAL DESCRIPTION C in January and 18.30 C in July. The amounts of precipitation, available mois­ Physiography ture, and the resulting distribution of vegetation zones within the Madrean Archipelago are influ­ The five mountain ranges are within the enced by mountain physiography. Elevation mountain subdivision of the Basin and Range affects precipitation and temperature; however, Geological Province that crosses Arizona in a Lowe (1961) indicated that mountain geomass is northwest to southeast belt (Wilson 1962). The more important than elevation in determining Province is characterized by elongated mountain vegetation. He reported a different vertical dis­ ranges trending northwest to southeast, separated placement of vegetation types and species on by broad, generally alluvial valleys (Nations and adjacent peaks of different mass. He referred to Stump 1981}0 Peaks range from Mt. Lemmon in this phenomenon as the Merriam effect. This may the Santa Catalina Mountains with an elevation of be one reason for the absence of Engelmann 2,791 m to Mt. Graham, the highest peak in the spruce (Picea engelmannil) at 2,740 m in the Santa zone, with an elevation of 3,265 m. Mt. Graham is Catalina Mountains, while it is common at that over 2,377 m above the Gila Valley at Safford. elevation in the more massive Pinaleno Moun­ Most other peaks in the region do not extend tains (Lowe 1961). Gehlbach (1981) stated that less above 2,438 m. The ranges tend to be elongated, massive mountains tend to be more arid. He indi-

153 cated that because the Huachuca Mountains are shallow, gravelly and cobbly, moderately coarse to lower and a third smaller in area than the Chirica­ moderately fine-textured. Slopes are variable; hua Mountains, coniferous forests are displaced rock outcrops are found in the hills and moun­ 305 m upward there. The Merriam effect may be tains. They usually support woodlands of oak, related to drying winds (Hanks and Dick-Peddie pinyon, and juniper. The Huachuca Mountains 1974), or to the infl uence of geomass on contain some areas of the Casto-Martinez-Canelo orographic precipitation. Gehlbach (1981) indi­ Association. These soils are found on mesas and cated that mass may be linked to the speed that valley slopes between 1,675 and 1,890 m in eleva­ mountains heat and cool during the summer, tion, and are deep, gravelly, moderately fine or since slower changes reduce evaporation rates fine-textured. The Casto and Canelo soils support and allow for more efficient utilization of summer woodlands while the Martinez soils support moisture. grasslands. The Casto and Martinez soils are Udic Haplustalfs and the Canelo is an Aeric Ochraqualf. Geology and Soils Hendricks (1985) identified Frigid Subhumid soils at the highest elevations in the Pinaleno and The mountains of the Madrean Archipelago Santa Catalina Mountains. These soils occur at consist of tilted, and sometimes structurally de­ elevations of from 2,075 to 3,290 m, where the formed blocks of rocks that are bounded by faults mean annual soil temperature is less than 8.30 C and have been severely eroded (Nations and and mean annual precipitation is over 405 mm. Stump 1981). Precambrian and Tertiary granites They are associated with pine, mixed conifer, and are common in the Basin and Range Province, as spruce-fir forests, and are representative of the are volcanic rocks from the Mesozoic to Quater­ Mirabal-Baldy-Rock Outcrop Association. The nary (Hendricks 1985). The Chiricahua Mountains soils are classified as Typic U storthents and Typic were an important volcanic center about 26 mil­ Cryorthents, and are shallow to deep, gravelly lion years ago, characterized by explosive and cobbly, and moderately coarse-textured; rock production of large quantities of ash and the for­ outcrops are characteristic of some sites. mation of caldera complexes (Nations and Stump 1981). The orogeny which had the greatest impact on the Province began about 13 million years ago, FOREST AND WOODLAND VEGETATION and may have ended in southeasterll Arizona about 6 to 3 million years ago (Hendricks 1985). General Distribution Patterns Mountain soils within the Province are gener­ ally shallow, rocky and gravelly (Hendricks 1985). The elevational zonation of woodlands and Soil development depends on parent material and forests within the Madrean Archipelago has been erosional surface stability. Weathering of granitic described by a number of authors (Lowe 1964, material tends to produce soils with coarse sur­ Whittaker and Niering 1965, Brady and Bonham face material and little profile development, and 1976, Gehlbach 1981, Niering and Lowe 1984, subsurface soils that are gravelly sandy loams or Hendricks 1985, Bahre 1991). Whittaker and Nier­ gravelly loams. Volcanic rocks weather into fine­ ing (1965) and Niering and Lowe (1984), in their grained material; soil development depends studies on a south slope of the Santa Catalina largely upon erosional dynamics on the site, al­ Mountains and in the highest elevations of the Pi­ though relatively deep soils are possible where naleno Mountains, listed the plant communities particle removal is low. Higher elevation moun­ and their elevational distributions. These can be tain soils tend to be more acidic and contain more regrouped, based on Niering and Lowe (1984), as: organic matter than soils at lower elevations. Sonoran Desert scrub (below 1,220 m), semi-de­ Hendricks (1985) classified most of the soils sert grassland (1,220 to 1,700 m), open oak within the five mountain ranges as Mesic Subhu­ woodland (1,400 to 1,700 m),- pygmy conifer-oak mid soils. These soils are found at about 2,135 m woodlands (1,520 to 2,130 m), pinyon-oak wood­ in southeastern Arizona, where mean annual soil land (1,830-2,130 m), Chihuahua pine-oak temperatures of 8.3 to 15.00 C and more than 405 woodlands (1,830 to 2,130 m), ponderosa pine-oak mm of mean annual precipitation occur. Most of forest (2,130 to 2,440 m), ponderosa pine forest these soils, except for some areas in the Huachuca (2,440 to 2,740 m), montane fir forest (2,440 to Range, are within the Lithic Haplustolls-Lithic Ar­ 2,740), mixed conifer forest (2,740 to 2,920 m) and giustolls-Rock Outcrop Association. The soils are subalpine forest communities (above 2,920 m).

154 Whittaker and Niering (1965) indicated how Historical community distribution also varied by aspect. The drier the site, the higher the elevational displace­ Fire, wind, and insects are the main natural ment. Species distribution patterns by aspect and disturbances in the region. Changes in the charac­ elevation in the Huachuca Mountains and in the teristics and timing of natural fires affect the Santa Catalina Mountains are similar (Brady and current distribution of vegetation zones. Increased Bonham 1976), although there appear to be differ­ fires during the Hypsithermal may have elimi­ ences between the Huachuca and Chiricahua nated some vegetation types on marginal sites Mountains (Gehlbach 1981). In the current review, Oones and Rietveld 1974}. American Indians prob­ we have grouped Niering and Lowe's open oak ably set some fires, but lightning was the main and Chihuahua pine-oak woodland as the encinal factor. Most fires were localized or ground fires woodlands, the pygmy conifer-oak and pinyon­ that tended to reduce understory vegetation. For­ oak woodlands as the pinyon-juniper woodlands, ests and woodlands were less densely stocked and the five forest zones together as the high ele­ with trees prior to European settlement (Moody et vation coniferous forests. a!. 1992, Covington and Moore 1994). Fire sup­ pression has eliminated most fires and allowed for potentially dangerous fuel accumulations and fire ladders to develop. Stand replacing crown VEGETATION CHANGES OVER TIME fires are becoming more common because of these changes (Covington and Moore 1994). Prior to European settlement, under natural fire Biogeography regimes, upper mixed conifer forests may have con­ tained less spruce, and ponderosa pine (Pinus The current distribution of woodlands and ponderosa) forests less Douglas-fir (Pseudotsuga forests on the isolated mountains of the region is menziesii var. glauca). Overgrazing in the wood­ the result of shifts in the climate conditions over lands, which eliminated the herbaceous layer, also the past 24,000 years Oackson 1970}. Merrill and prevented the spread of wildfires and reduced com­ Pewe (1977) indicated that temperatures in the petition for tree establishment. The movement of Southwest were 5 to 6° C cooler and precipitation oaks and junipers into grasslands and the increased was 20 to 25 percent greater during the late Qua­ tree densities in juniper savannahs have been attrib­ ternary when glaciers occurred on Mount paldy in uted to these two factors. the White Mountains (8,000 to 35,000 B.P.). Pa­ Although there are a large number of forest lynological evidence from the Willcox Playa insect species within the area, they were not con­ indicates a vertical displacement of vegetation sidered to be a major problem (Shupe and zones of at least 915 to 1,220 m during pluvial Solether 1973), although the evaluation may be times (Hevly and Martin 1961). This displacement different now, especially on M t. Graham. Wind allowed Rocky Mountain forest flora to spread may have had a significant impact within the co­ from the Colorado Plateau into the sub-Mogollon niferous forests. mountain ranges and into the Sierra Madre Occi­ dental. The changing distributions of vegetation types in the Southwest over the past 22,000 years HUMAN USE OF FORESTS AND and their relationships to climate have been docu­ WOODLANDS ment by analyses of packrat (Neotoma spp.) middens (Van Devender and Spaulding 1979). The encinal woodlands of the Madrean Archi­ The Hypsithermal Interval, also called the pelago have been important to prehistoric and Medieval Warm Period, brought warmer and historic people (Propper 1992). The prehistoric drier conditions and a rise in the elevational dis­ people gathered acorns for food and ceremonial tribution of vegetation zones; the vegetational purposes, and pinyon nuts and juniper berries for links between mountain ranges and the Colorado winter food. American Indians also collected fuel­ Plateau were broken and xerophytic species in­ wood and construction materials and hunted vaded the lower elevations within the Basin and game in the woodlands and forests. Range Province. Climatic conditions over the past The Apache Indians and Spaniards entered 4,000 years have been moderately cool and moist the region in the late 1600 (Propper 1992). The although extended periods of drought have oc­ Spanish used the wooded areas primarily for fuel­ curred Oackson 1970). wood and construction material for their homes,

155 mines, and ranching activities. However, inten­ tion have been employed (Gottfried and Ffolliott sive development in the region did not begin until 1993). the 1870s and 1880s, when hostilities with the Annual precipitation in the woodlands ex­ Apaches began to decline and the railroad entered ceeds 405 mm; generally, half falls during the the region. Large herds of cattle were moved into growing season of May through August. Extremes the area from Texas and Sonora during this pe­ in annual precipitation range from 305 to over riod; Bahre (1991) indicated that there were over 1,015 m. Freezing temperatures are rare in the 200 ,000 head in southeastern Arizona in 1890. The southern portions of the woodlands but increase major impact on the woodlands during the late 19 to an average of almost 125 days at the northern century was the cutting of wood to support min­ limits. ing activities. The Tombstone Mining Region The woodlands occur between 1,200 and 2,200 contained over 50 silver mines and 7 stamp mills m in elevation. Structural development of the enc­ in 1878 (Bahre 1991). Fuelwood, mostly oak (Quer­ inals is apparently determined by soil type and cus spp.), pinyon, juniper Uuniperus spp.), and depth. Stands commonly are located in a variety mesquite (Prosopis juliflora), was cut to run the of sites including along drainages, on rocky steam engines and meet the cooking and heating slopes, and on alluvial basin fill and fans (USDA needs of the inhabitants (Bahre 1991). Over-cut­ Forest Service 1987). ting adjacent to settlements caused fuelwood shortages that resulted in increased transportation costs to bring in supplies from more distant mountains and in increased prices. Characteristics Sawmills in the Santa Rita Mountains sup­ plied ponderosa pine and Douglas-fir to Tucson A large variety of oak species are found in the and neighboring mines before 1870. Logging be­ encinal woodlands. Mexican blue (Q. oblongifolia) gan in the other mountain ranges after the is found at the lowest elevations to the north. settlement of the Upper Gila Valley and the begin­ Among the oaks in the mountainous regions of ning of the mining booms. The Huachuca and southeastern Arizona, southwestern New Mexico, Chiricahua Mountains supplied much of the con­ and Texas are Emory (Q. emoryi), Arizona white struction timber for Tombstone. Historic records (Q. arizonica), Mexican blue, and gray (Q. grisea). indicate that only the five largest mountain ranges Silverleaf oak (Q. hypoleucoides) and netleaf oak had significant logging activities, mostly prior to (Q. rugosa) are found at the intermediate eleva­ 1900 (Bahre 1991). Only the Pinaleno"and Santa tions. Border pinyon (P. discolor) and juniper Catalina Mountains have had limited harvesting species are found intermixed with the oaks on since that time. Most of the logging in the Pi­ many sites throughout the encinals. Other impor­ naleno Mountains occurred after 1893; however, tant pines within the encinal woodlands are: early activities were confined to isolated pockets Chihuahua pine (Pinus leiophylla var. chihuahuana) of timber on the lower third of the mountain and Apache pine (P. engelmannii). (Shupe and Solether 1973). At its upper elevations in the southwestern United States and in Mexico, the encinals often grade into the interior ponderosa pine type. They ENCINAL WOODLANDS can merge with the pinyon-juniper woodlands with complex transitional forms. Information on the distribution, charac­ Encinal woodlands contain relatively small, teristics, and uses of encinal woodlands of the often multiple-stemmed, irregularly formed trees. southwestern United States and northern Mexico Species compositions and stand densities depend has been obtained largely from Brown (1982). The largely upon specific site characteristics (Gottfried encinals, also referred to as the Madrean ever­ and Ffolliott 1993). One-, two-, or occasionally green woodland formation (Brown and Lowe three-aged stand structures are found. Intermin­ 1980), are concentrated in the Sierra Madre Occi­ gled with these trees are shrubs, grasses and dental of Mexico, from where they extend grass-like plants, forbs, and succulents, often in northward into southeastern Arizona, southern parks and savanna-like mosaics. Stand density is New Mexico, and Texas. Encinal woodlands cover relab~d to soil properties, site characteristics, and approximately 80,300 km2 in aggregate, although fire and land use histories. a precise delineation of this biotic community is Tree densities in the encinals vary consider­ difficult, since inconsistent criteria for classifica- ably. The numbers of trees range from a few

156 scattered individuals to several hundred forniarum var. fallax, also is found in the pinyon­ stems/ha. Volumes of stemwood vary from less juniper stands located south of the Mogollon Rim, than 2 to over 100 m3 /ha (Ffolliott and Gottfried including parts of the Madrean Archipelago. The 1992). Annual growth rate is relatively slow, rang­ Mexican pinyon (P. cembroides) is widespread at ing from 0.25 to 0.50 m3/ha, an annual growth lower elevations in the mountains of northern rate of less than 1 percent. Mortality generally is Mexico, (Critchfield and Little 1966), and in the low, likely because the long history of utilization rain shadows of the eastern and western Sierra in some areas has reduced the number of old trees Madre mountain ranges (Segura and Snook 1992). (Conner et al. 1990). Border pinyon is often classified as Mexican pin­ Twelve habitat types in the Southwest are yon in some of the older literature. dominated by encinal oak species (USDA Forest Junipers are the other major tree group in the Service 1987). A predominant habitat type of the southwestern woodlands. The major species in the encinals in southeastern Arizona is Quercus emo­ Madrean Archipelago are: alligator (J. deppeana), ryi / Bouteloua curtipendula. In addition, a general one-seed (J. monosperma), and red berry juniper (J. scarp woodland habitat type is recognized on erythrocarpa). Utah (J. osteosperma) and Rocky sites with slopes in excess of 40 percent. Mountain (J. scopulorum) are important in other parts of the Southwest. Alligator juniper is an im­ portant component of many encinal stands in the PINYON-JUNIPER WOODLANDS southwestern United States and in the Mexican pinyon forests. Red berry juniper (J. erythrocarpa) Pinyon-juniper woodlands cover approxi­ is found on drier sites in southern Arizona and mately 19 million hectares in the western United New Mexico. States. The climate in the woodlands is classified A typical pinyon-juniper stand in the South­ as arid or dry sub-humid (Gottfried and Ffolliott west is uneven-aged and contains about 1,150 1993). In the Southwest, stands generally are trees and 21 m 2 of basal area per hectare (Barger found at elevations from 1,370 to 2,290 m where and Ffolliott 1972). Niering and Lowe (1984) re­ annual precipitation ranges from 305 to 560 mm. ported that an average Mexican pine-oak Although Whittaker and Niering (1965) and woodland on the south slope of the Santa Catalina Niering and Lowe (1984) did not identify a sepa­ Mountains contained 1,124 trees/ha. Although rate a pinyon-juniper community, these stands are oak species dominated the smaller size classes, 46 unique and easily differentiated. Pollisco et al. percent of the total number of trees and 95 percent (this volume), in a study of woodlands in three of the trees 15 cm and larger at breast height (bh) Sky Island mountain ranges, found numerous were pinyon and alligator juniper. Pinyons are sites where pinyon and juniper constituted at least more common in a typical stand in the Southwest 80 percent of the tree basal area. The seasonal dis­ and tend to dominate in the smaller size classes, tribution of precipitation, particularly the relative while junipers are an important component of the amounts of winter and summer moisture, influ­ larger size classes and contribute almost half of ences stand composition. The woodlands grade the wood volume. However, some pinyons in the into grasslands, brushlands, and encinal wood­ Santa Catalina Mountains were over 60 em in di­ lands on drier sites, and into ponderosa pine ameter (Niering and Lowe 1984). Even-aged forests on more moist sites. They are found on stands develop after disturbances such as fire and soils associated with different parent materials tree control operations for range improvement or and characterized as being shallow, well-drained, agricultural activities. and generally of low fertility, although exceptions Pinyon-juniper woodlands are not homogene­ occur. ous and consist of a large number of habitat types or plant associations (Moir and Carleton 1987). The USDA Forest Service (1987), for example, rec­ Characteristics ognizes six habitat types in southern Arizona and New Mexico where border pinyon dominates and Although the two-needled Colorado pinyon four where either alligator or red berry junipers (P. edulis) is the most characteristic pinyon of the dominate. Available soil moisture is the most criti­ woodlands of the Southwest, the three-needled cal factor controlling the distribution of border pinyon is associated with most pinyon-ju­ woodlands, and the composition and density on niper and encinal woodlands of southern Arizona undisturbed sites. Junipers, which are more and New Mexico. A single-needled pinyon, P. cali- drought-tolerant than pinyon, dominate on drier

157 sites, but pinyons increase in importance as avail­ spruce-fir, mixed conifer, and ponderosa pine for­ able moisture increases. The distribution of ests respectively correspond to Merriam's juniper species is influenced by the proportion of Hudsonian, Canadian, and Transition Life-zones winter precipitation. Alligator, one-seed, red (Lowe 1964). berry, and Rocky Mountain junipers dominate in summer moisture areas, while Utah juniper oc­ curs in winter moisture areas. Temperature Habitat Types extremes also affect the upper and lower eleva­ tional distribution of woodland species. The USDA Forest Service (1987) recognizes a large number of forest habitat types within south­ eastern Arizona that are found at a variety of THE HIGH ELEVATION CONIFEROUS elevations and in different mountains. For exam­ FORESTS ple, a partial list of spruce-fir habitat types would include: Community Distribution Abies Jasiocarpa / Carex loenea 3,050 m Pinaleno A. Jasiocarpa / Erigeron eximius 2,865-3,110 m Pinaleno A. Jasiocarpa / /amesia americana 4650 m Catalina High elevation coniferous forests generally oc­ A. Jasiocarpa /moss 2,985-3,505 m Pinaleno cur above 2,130 m. Niering and Lowe (1984) Picea enselmannii / Acer 8Jabrum 2,745 m Chiricahua recognized six community types in the Santa Some other common habitat types are Catalina Mountains and an additional two types Pseudotsuga menziesii/Quercus hypoJeucoides, in the higher Pinaleno Mountains. Spruce-fir for­ which is found in the Chiricahua, Pinaleno, ests, which are confined to the highest elevations Huachuca, and Animas Mountains between 1,980 within the Pinaleno Mountains, contain Engel­ to 2,620 m, and Pinus ponderosa/ Quercus hy­ mann spruce and corkbark fir (Abies Jasiocarpa poJeucoides, which is found in the Chiricahua, var. arizonica). These are usually found above Pinaleno, Santa Rita, Santa Catalina, and Galiuro 2,920 m. Mixed conifer forests, which includes Mountains between 2,100 and 2,450 m. montane forest communities described by Niering and Lowe (1984), are found from 2,440 to 2,920 m. These are diverse forests that can contain up to Amount of Area Covered by Forest seven major tree species: Douglas-fir, Engelmann spruce, corkbark fir, white fir (A. concoJor), pon­ Almost all of the forests within the United derosa pine, southwestern white pine (P. States portion of the Madrean Archipelago are ad­ strobiformis), and quaking aspen (PopuJus tremu­ ministered by the Coronado National Forest. Joides). The mix of species and habitat types will There are about approximately 2,020 ha in the vary throughout the Madrean Archipelago. Cork­ Santa Catalina and 4,050 ha in the Chiricahua bark fir, for example, is found at one location in Mountains that could be classified as commercial the Santa Catalina Mountains, where it occurs forest based on stand conditions and accessibility with aspen, Douglas-fir, and white fir, and is ab­ (Shupe and Solether 1973). The Pinaleno Moun­ sent in the Santa Rita, Chiricahua, and Huachuca tains contain 3,410 ha of operable commercial Mountains. Some mixed conifer stands can be forest land, including 440 ha of ponderosa pine, dominated by Douglas-fir and white fir with mi­ 2,260 ha of mixed conifer, and 710 ha of spruce-fir; nor components of other tree species. in addition, there are 1,920 ha of commercial for­ The third major category of forests is domi­ est that is inoperable (Shupe and Solether 1973). nated by ponderosa pine and is found from 2,130 The Pinaleno Mountains also contain pockets of to 2,740 m. Silverleaf and Arizona oaks are com­ forest vegetation and forested steep slopes and mon in pine stands between 2,130 and 2,440 m, rocklands that are not commercially operable. while Gambel oak (Quercus gambeJh) is common at elevations between 2,440 and 2,740 m. South­ western white pine with some Douglas-fir are Stand Characteristics found in stands between 2,590 and 2,740 m (Nier­ ing and Lowe 1984). The five-needled Arizona A typical spruce-fir stand in the Pinaleno ponderosa pine (P. ponderosa var. arizonica, also Mountains contains approximately 2,773 conifer classified as P. arizonica) replaces the Rocky and aspen trees/ha that are 2.5 cm dbh and larger; Mountain variety (P. ponderosa var. scopuJorum) 95 percent of the stand consists of corkbark fir and on many southern Arizona sites (Lowe 1964). The spruce, in almost equal proportions (Niering and

158 Lowe 1984}. However, the proportions of spruce management goals are to be achieved. Managers, and fir vary depending on the stage of develop­ with public input, must determine the desired fu­ ment following major disturbance (Stromberg and ture condition and mix of resources to be favored Patten 1991). In old-growth stands, spruce will on a site, and modify their prescriptions. have a greater basal area and density of large trees, while corkbark fir will dominate the smaller trees and sapling size classes (Niering and Lowe Encinal Woodlands 1984, Stromberg and Patten 1991). Thirteen per­ cent of the spruce in the N iering and Lowe Ecological research to support silvicultural sample, for example, were greater than 30 cm, prescriptions in the encinal woodlands, is rela­ while only 2 percent of the fir was in the larger tively limited (McPherson 1992). Natural size classes. regeneration from seed is apparently episodic; The mixed conifer forest in the Pinaleno oak seedlings were 19 percent of the regeneration Mountains contained about 2,330 trees per hectare in one study; sprouting from roots and stumps (Niering and Lowe 1984). Over 50 percent of the was a more common regenerative mechanism average stand consisted of white fir, mainly be­ (Borelli et al. 1994). Only nine percent of the plots cause of the large number of trees in the smaller contained any tree regeneration, and, as a conse­ dbh classes (less than 15 cm). Spruce and fir com­ quence, the encinals might not be reproducing in prised 34 percent of the density, and Douglas-fir sufficient numbers to sustain themselves if they was about 10 percent. Some of the old-growth continue to be heavily harvested (Borelli et al. Douglas-fir had diameters of 152 to 178 cm (Shupe 1994). On many sites, encinal stands sprout vigor­ and Solether 1973). ously after cutting, indicating that coppicing The Douglas-fir and white fir forest in the might form a basis to obtain regeneration in Santa Catalina Mountains only contained 455 silvkultural prescriptions. Furthermore, harvest­ conifers/ha but supported an additional 425 ing cycles can be reduced through proper trees/ha of Acer spp., /amesia americana, and Ro­ thinning of the resultant coppice (Touchan et al. binia neomexicana. The ponderosa pine forest 1992). Sustainability of vegetative reproduction is contained 1,375 conifers fha, 74 percent ponderosa unknown, however. pine and the other being southwestern white pine, A silvicultural prescription for sustained pro­ Douglas-fir and white fir. Oaks and Robinia made ductivity of fuelwood, based largely upon on the up an additional 450 trees/ha. studies mentioned above and management proce­ d ures of the USDA Forest Service in southeastern Arizona, might involve the following scenario. SILVICULTURE Trees to be harvested are marked for removal by managers (Bennett 1992). A subsequent thinning of the resultant coppice to retain 1, 2, or 3 of the Silviculture Prescriptions largest and most vigorous residuals is scheduled for 5 years after harvesting. Delaying thinning be­ One part of the definition of silviculture states yond this time can reduce growth of the residuals that it is the application of a knowledge of silvics (Touchan et al. 1992). Residual trees are selected to the treatment of a forest or woodland (Gottfried for harvesting after they attain a specified size. and Ffolliott 1993). One key objective of tradi­ For example, a diameter of 15 to 20 centimeters tional silviculture is to ensure adequate tree drc (diameter at root collar) likely can be reached regeneration for the future. There is growing in­ in 20 to 30 years after the coppice thinning on terest and public demand for ecosystem some sites. The USDA Forest Service specifies a management that will create and maintain healthy 15-centimeter stump height and about a 45-centi­ and sustainable forest and woodland ecosystems. meter slash height in southeastern Arizona. Other Health is defined as the ability of a forest to re­ silvicultural prescriptions based upon clearcut­ cover from natural or human-caused stressors ting, shelterwood, seed tree, and selection (Haack and Byler 1993), while sustainability refers cuttings have not been widely tested. to the long-term production of all forest values. Removal of trees in any silvicultural treat­ Silviculture is a tool for ecosystem or multire­ ment changes landscape diversity, which can source management of any forest or woodland affect habitats for wildlife. Unfortunately, there ecosystem. Silvics or tree ecology must serve as have been no studies on the effects of harvesting the basis for management activities if ecosystem in encinal woodlands on deer habitats (Smith and

159 Anthony 1992) or those of other big game species, However, there are some disadvantages with both although an increase in diversity might be benefi­ methods, especially the costs associated with in­ cial if sufficient cover is retained. Encinal tensi ve management and potential damage to woodlands provide resources for unique assem­ residual trees during subsequent harvests. Bassett blages of neotropical migratory birds (Block et al. (1987) discussed the trade-offs that must be evalu­ 1992), and it is likely that different management ated in preparing a silvicultural prescription. approaches will be needed for different situations. Success from a forestry perspective will depend Actual impacts of silvicultural treatments on non­ largely upon achieving satisfactory regeneration. game bird and many other wildlife species remain The shelterwood method is used to regenerate to be evaluated. even-aged stands and can be used in existing Although livestock production is important, even-aged and uneven-aged pinyon-juniper encinal woodlands have not been subjected to woodlands. Bassett (1987) recommended the two­ large-scale range improvement practices (Ffolliott step shelterwood method. A modified one-cut and Guertin 1987, McClaran et al. 1992). Haworth shelterwood method, which removes the entire and McPherson (1994) indicated that production overstory, can be used where advance tree regen­ levels and species compositions of herbaceous eration is satisfactory. However, it is important to plants might not be affected greatly by range im­ protect the younger trees from harvesting dam­ provement practices consisting of the removal of age. trees in fuelwood harvesting. However, more re­ Bassett's (1987) recommendations are valid search is necessary to assess overstory-understory for stands within the Madrean Archipelago, espe­ relationships over the broad range of sites found cially if regeneration of pine or non-sprouting in the encinal woodlands (McPherson 1992). juniper species is important. The clearcut or seed­ tree methods would favor alligator juniper and oak regeneration, but generally result in unsatis­ Pinyon-juniper Woodlands factory regeneration of species with short seed dispersal distances. Although knowledge of pinyon-juniper wood­ Current management is attempting to inte­ land ecology is increasing, it still is incomplete grate livestock and wildlife with tree production (Gottfried and Ffolliott 1993). However, managers (Gottfried and Severson 1993). Silvicultural meth­ recognize that heavy, wingless seeds of pinyons ods can also be used to enhance forage production and junipers, and dryland environmental condi­ for livestock and forage and cover for wildlife. A tions require special considerat1on when comrnon treatment is designed to clear small dis­ preparing silvicultural prescriptions. It would be persed areas of trees. This practice has been ideal if treatments could be linked to good seed sho",'n to benefit elk (Cervus eZaphus) and mule crops, but this is difficult considering the rela­ deer (Odocoileus hemionus) (Short et al. 1977). tively long period between good years, and the However, care must be taken to insure that open­ inability to confidently forecast them. Silvicultural ings are not too large (Gottfried and Severson prescriptions must be linked to habitat type in or­ 1993) or that the woodlands not become too frag­ der to succeed. mented. Wildlife and other needs must be Bassett (1987), in reviewing the potential ap­ assessed to ensure tradeoffs in resource allocation plicability of common silvicultural prescriptions are acceptable. Openings create a more diverse to pinyon-juniper woodlands in the Southwest, landscape that should favor other wildlife species concluded that single-tree selection and two-step such as small mammals (Gottfried and Severson shelterwood methods best sustain stand health 1993). In many cases, the size of the openings and productivity for tree products or for a mix of might not be critical, if continuous corridors of resources. These cutting methods are compatible adequate width are maintained. Managers must with the dispersal patterns of heavy tree seed, decide if cleared wildlife-livestock openings provide protected micro-sites for regeneration, should be maintained, or trees should be allowed and are esthetically acceptable. The single-tree se­ to reoccupy the sites. A management scheme lection method reduces stand density, but still could be created which would involve a variety of retains the uneven-aged structure and horizontal seral stands in space and time. This strategy and vertical diversity important for some wildlife wou1d enhance biological diversity within wood­ species. Initial harvesting by the shelterwood land landscapes. method, which leaves the best trees for seed pro­ Treatments that reduce tree densities should duction, also tends to retain a diverse cover. benefit livestock and native ungulates by provid-

160 ing additional forage while maintaining thermal group selection prescription (Shupe and Solether and hiding cover. However, the impacts of resid­ 1973). Many of the Mt. Graham stands are fairly ual trees on understory dynamics are unclear. old and natural mortality is increasing; individual Some questions concern the quantity and quality tree growth is also lower in dense stands. The goal of herbaceous vegetation which can be achieved, was to maintain tree vigor and reduce insect and and the longevity of any increases. Relationships disease damage. These prescriptions may not be among overstory cover, tree regeneration, and for­ feasible today unless there is a market for the tim­ age yields need better definition. ber. More importantly, public attitudes do not support commercial harvesting solely for wood products; harvesting would have to be related to forest health considerations. Slash cleanup to reduce fire hazard was an Conifer Forests important component of most treatments (Shupe and Solether 1973). Slash disposal policies are un­ The only remaining commercial forests in the der review, since ecosystem benefits must be United States portion of the Madrean Archipel­ compared to increased fire and insect hazards. ago are found in the Santa Catalina, Chiricahua, However, Moody et al. (1992) indicate that a high and Pinaleno Mountains (Shupe and Solether percentage of the forest on the Coronado National 1973). However, because of conflicting land uses Forest is at high risk of catastrophic wildfires be­ in the Santa Catalina Mountains and poor site cause of high fuel loading and lack of and low stand densities in the Chiricahua management to alleviate the situation. If condi­ Mountains, these two areas could not support a tions have changed drastically since 1973, the commercial timber management program. The Forest Service may have to evaluate the need for Pinaleno Mountains contain commercial stands fuel reduction activities, sanitation or salvage log­ of spruce-fir, mixed conifer, and ponderosa pine. ging, and eventually, prescribed fire. The latter The silviculture of these forest types in the cen­ would be difficult because of the fuel loading and tral and southern Rocky Mountains has been fuel ladders. Any activities to correct the condi­ reviewed by Alexander (1974). This review cov­ tion would draw public comment. ered the various even-aged and uneven-aged Insect and fire control activities in the old­ systems that are applicable to achieve satisfac­ growth stands within non-wilderness areas will tory regeneration of these forests. Silviculture also have to be evaluated. The public may endorse for multiple-use was covered, but in less detail. natural forest dynamics in a remote wilderness Shupe and Solether (1973) indicated that the area but be less tolerant when they can see its mos~ successful regeneration prescriptions on effects on their way to a favorite campground. Mount Graham were light selection cuts or small Large areas of dead and dying trees or of burned patch clearcuts of from 0.8 to 2.0 ha. Blowdown snags often are the results of unhealthy stand con­ was a problem in some stands if overstory remov­ ditions. Silvicultural treatments may become_ als were heavy, and dwarf mistletoe necessary to open dense stands where tree vigor, (Arceuthobium vaginatum var. cryptopodum) and resistance to insects and diseases, has been was a problem in some ponderosa pine stands. reduced or where unacceptable insect and disease Ice damage has been a periodic problem. Multi­ damage has been identified. Regeneration or im­ ple-use silviculture for a variety of resources provement treatments would be used to improve and for sustained stand health is the main con­ stand health prior to insect or disease attack, cern in the Sky Islands today. The USDA Forest while sanitation treatments would be used to pre­ Service overall management objective for Mount vent a pest from spreading. Graham is to maintain and enhance esthetics The roundheaded pine beetle (Dendroctonus and outdoor recreational values (Shupe and adjunctus) currently is causing considerable mor­ Solether 1973). tality in ponderosa pine forests on Mount Silvicultural treatments anticipated in 1973 Graham, especially adjacent to Riggs Lake. Coro­ were: salvage of poor risk and overmature trees; nado National Forest crews have cut infected and light commercial thinning of sawtimber and sub­ dead trees in hopes of removing potential hazards sawtimber stands; overstory removal (simulated and containing the problem. Many cut trees have shelterwood) where satisfactory regeneration has been bucked and left as firewood for recreational become established under overmature trees; and visitors. Some were sold to a sawmill in Alamo­ stand regeneration according to a single-tree or gordo, New Mexico.

161 CONCLUSIONS Southwest. In: Ffolliott, P.F.; Gottfried, G.J.; Bennett, D.A.; Hernandez C., V.M.; Ortega-Rubio, A.; Hamre, The mountains of the Madrean Archipelago R.H., tech.coords.Ecology and management of oak and or Sky Islands support a diverse mixture of forest associated woodlands: perspectives in the southwest­ and woodland ecosystems representing the Rocky ern United States and northern Mexico; 1992 April 27-30; Sierra Vista, AZ. Gen. Tech. Rep. RM-218. Fort Mountain and Madrean floras. Regional and local Collins, CO: US. Department of Agriculture, Forest climatic conditions over last 24,000 years have in­ Service, Rocky Mountain Forest and Range Experiment fluenced the present distribution of vegetation Station: 65-70. communities. These lands have been used by hu­ Borelli, Simone; Ffolliott, Peter F.; Gottfried, GeraldJ.1994. mans since prehistoric times. Natural regeneration in encinal woodlands of south­ Demands for the forest and woodland re­ eastern Arizona. The Southwestern Naturalist. 39: sources have changed over time. However, there 179-183. currently are conflicts among different interest Brady, Ward; Bonham, Charles D .1976. Vegetation patterns groups as to how intensively the land should be on an altitudinal gradient, Huachuca Mountains, Ari­ managed. To this end, silvicultural prescriptions, zona. The Southwestern Naturalist.21: 55-66. matched to habitat type, provide one tool for eco­ Brown, David E. 1982. Madrean evergreen woodland. In: system management in the Madrean Archipelago. Biotic communities of the American southwest-United Sta tes and Mexico. Desert Plants .4:59-65. The Coronado National Forest is charged with Brown, D. E.; Lowe, C. H. 1980. Biotic communities of the ecosystem management that will ensure sustain­ Southwest. Gen. Tech. Rep. RM-78. Fort Collins, CO: ability and health of the region's forests and U.S. Department of Agriculture, Forest Service, Rocky woodlands. The various interest groups should Mountain Forest and Range Experiment Station. 1 p. work together to achieve these goals. Conner, Roger C.; Born, J. David; Green, Alan W.; O'Brien, Renee A. 1990. Forest resources of Arizona. Res. Bull. INT-69. Ogden, UT: US. Department of Agriculture, LITERATURE CITED Forest Service, In termountain Research Sta tion. 92 p . Covington, W. Wallace; Moore, Margaret M. 1994. South­ Alexander, Robert R. 1974. Silviculture of the central and western ponderosa forest structure: changes since southern Rocky Mountain forests: a summary of the Euro-American settlement. Journal of Forestry. 92: 39- status of our knowledge by timber types. Research 47. Paper RM-120. Fort Collins, CO: US. Department of Critchfield, William B.; Little, Elbert L.Jr.1966. Geographic Agricul ture, Forest Service, Rocky Mountain Forest and distribution of the pines of the world. Misc. Pub. 991. Range ExperimentStation. 36 p. .. Washington, DC: US. Department of Agriculture, For­ Bahre, Conrad Joseph. 1991. A legacy of change: historic estService. 97 p. human impact on vegetation of the Arizona border­ Ffolliott, Peter F.; Gottfried, Gerald J. 1992. Growth, yield, lands. University of Arizona Press, Tucson. 231 p. and utilization of oak woodlands in the southwestern Barger, Roland L.; Ffolliott, Peter F. 1972. Physical charac­ United States. In: Ffolliott, P.P.; Gottfried, G.J.; Bennett, teristics and utilization of major woodland tree species D. A.; Hernandez C., V.M.; Ortega-Rubio, A.; Hamre, in Arizona. Res. Pap. RM-83. Fort Collins, CO: US. R.H., tech.coords.Ecology and management of oak and Department of Agriculture, Forest Service, Rocky associated woodlands: perspectives in the southwest­ Mountain Forest and Range Experiment Station. 80 p. ern United States and northern Mexico; 1992 April Bassett, Richard L. 1987. Silvicultural systems for pinyon­ 27-30; Sierra Vista, AZ. Gen. Tech. Rep. RM-218. Fort juniper. In: Everett, R.L., compiler. Proceedings, Collins, CO: US. Department of Agriculture, Forest Pinyon-juniper conference; 1986 January 13-16; Reno, Service, Rocky Mountain Forest and Range Experiment NV. Gen. Tech. Rep. INT-215. Ogden, UT: US. Depart­ Station: 34-38. ment of Agriculture, Forest Service, Intermountain Ffolliott, P. F.; Guertin, D. P.1987. Opportunities for multi­ Research Station: 273-278. ple use values in the encinal oak woodlands of North Bennett, Duane A.1992. Fuelwood extraction in southeast America. In: Aldon, E.P.; Gonzales Vicente, C.E.; Moir, Arizona. In: Ffolliott, P.F.; Gottfried, G.J.; Bennett, D. A.; W. H., tech. coords. Strategies for classification of natu­ Hernandez C., V.M.; Ortega-Rubio, A.; Hamre, R.H., ral vegetation for food production in arid zones; 1987 tech. coords. Ecology and management of oak and Odober 12-16; Tucson, AZ. Gen. Tech. Rep. RM-150. associated woodlands: perspectives in the southwest­ Fort Collins, CO: U.S. Department of Agriculture, For­ ern United States and northern Mexico; 1992 April est Service, Rocky Mountain Forest and Range 27-30; Sierra Vista, AZ. Gen. Tech. Rep. RM-218. Fort Experiment Station: 182-189. Collins, CO: US. Department of Agriculture, Forest Gehlbach, Frederick R.1981. Mountain islands and desert Service, Rocky Mountain Forest and Range Experiment seas: a natural history of the U S.-Mexican Borderlands. Station: 96-97. Texas A&MUniversityPress,College Station.298p. Block, W. M.; Ganey, J. L.; Severson, K. E.; Morrison, M. L. Gottfried, Gerald J. 1989. Effects of patch clearcutting on 1992. Use of oaks by neotropical migratory birds in the water yield improvement and on timber production in

162 an Arizona mixed conifer watershed. Ph.D. disserta­ Hernandez C., V.M.; Ortega-Rubio, A.; Hamre, R.H., tion, School of Renewable Natural Resources, tech. coords. Ecology and management of oak and University of Arizona, Tucson,184p. associated woodlands: perspectives in the southwest­ Gottfried, Gerald J.; Ffolliott, Peter F. 1993. Silvicultural ern United States and northern Mexico; 1992 April prescriptions for sustained productivity of southwest­ 27-30; Sierra Vista, AZ. Gen. Tech. Rep. RM-218. Fort ern pinyon-juniper and encinal woodlands. In: Collins, CO: U.S. Department of Agriculture, Forest Manzanilla, H.; Shaw, D.; Aguirre-Bravo, C.; Iglesias Service, Rocky Mountain Forest and Range Experiment Gutierrez, L.; Hamre, R.H., tech. coords. Making sus­ Station: 24-33. tainability operational: fourth Mexico/U.S. Merrill, Robert K.; Pewe, Troy L. 1977. Late Cenozoic Symposium; 1993 April 19-23; Santa Fe, NM. Gen. Tech. geology of the White Mountains, Arizona. Spec. Pap. Rep. RM-240. Fort Collins, CO: U.s. Department of No.1. Phoenix, AZ: Sta te of Arizona, Bureau of Geology Agricul ture, Forest Service, Rocky Mountain Forest and and Mining Technology. 65 p. Range ExperimentStation: 185-192. Moir, W. H.; Carleton, J. 0.1987. Classification of pinyon­ Gottfried, Gerald J.; Severson, Kieth E. 1993. Distribution juniper (P-J) sites on national forests in the Southwest. and multiresource management of pinyon-juniper In: Everett, R.L., compiler, Proceedings, Pinyon-juniper woodlands in the southwestern United States. In: Man­ conference; 1986 January 13-16; Reno, NV. Gen. Tech. aging pinon-juniper ecosystems for sustainability and Rep. INT-215. Ogden, UT: U.S. Department of Agricul­ social needs; 1993 April 26-30; Santa Fe, NM. Gen. Tech. ture, Forest Service, Intermountain Research Station: Rep. RM-236. Fort Collins, CO: U.S. Department of 216-226. Agriculture, Forest Service, Rocky Mountain Forest and Moody, Ron; Buchanan, Les; Melcher, Ron; Wistrand, Range ExperimentStation: 108-116. Hunter. 1992. Fire and forest health: Southwestern Re­ Haack, Robert A.; Byler, James W. 1993. Insects and patho­ gion. Unpublished Report. Albuquerque, NM: U.s. gens: regulators of forest ecosystems. Journal of Department of Agriculture, Forest Service, Southwest­ Forestry. 91: 32-37. ern Region. 38 p. Hanks, Jess P.; Dick-Peddie, W.A.1974. Vegetation patterns Nations, Dale; Stump, Edmund. 1981. Geology of Arizona. of the White Mountains, New Mexico. The Southwest­ Kendall/HuntPublishingCo., Dubuque,Iowa. 221 p. ern Naturalist. 18: 371-382. Niering, William A.; Lowe, Charles H. 1984. Vegetation of Haworth, Kathryn; McPherson, Guy R. 1994. Effects of the Santa Catalina Mountains: community types and Quercus emoryi on herbaceous vegetation in a semi arid dynamics. Vegetatio.58: 3-28. savanna. Vegetatio.112: 153-159. Pollisco, Roy R.; Ffolliott, Peter F.; Gottfried, Gerald J. Hendricks, David M. 1985. Arizona soils. University of Ecological conditions in the overlap of the pinyon-juni­ Arizona Press, Tucson. 244 p . per and encinal woodlands. In. Biodiversity and Hevly, Richard H.; Martin, Paul 5.1961. Geochronology of management of the Madrean Archipelago; 1994 Sep­ pluvial Lake Cochise, southern Arizona: I. Pollen anal y­ tember 19-23; Tucson, AZ. Gen. Tech. Rep. RM-XXX. sis of shore deposi ts . Journal of the Arizona Academ y of Fort Collins, CO: U.S. Department of Agriculture, For­ Sciences. 2: 24-31. est Service, Rocky Mountain Forest and Range Jackson, Earl. 1970. The natural history story of the Chi rica - Experiment Station. (This proceedings). hua National Monument. Southwest Parks and Propper, Judith G. 1992. CuI tura!, recreational, and esthetic Monuments Association, Globe, AZ. 76 p. values of oak woodlands. In: Ffolliott, P.P.; Gottfried, Jones, John R.; Rietveld, Willis J. 1974. Occurrence of Picea GJ.; Bennett, D.A.; Hernandez C., V.M.; Ortega-Rubio, pungens (Pinaceae) near Flagstaff, Arizona. The South­ A.; Hamre, R.H., tech. coords. Ecology and manage­ western Naturalist. 19:334-335. ment of oak and associated woodlands: perspectives in Lowe, Charles H. 1961. Biotic communities of the Sub-Mo­ the southwestern United States and northern Mexico; gollon Region of the inland Southwest. Journal of the 1992 April 27-30; Sierra Vista, AZ. Gen. Tech. Rep. Arizona Academ y of Sciences. 2: 40-49. RM-218. Fort Collins, CO: U.S. Department of Agricul­ Lowe, Charles H. 1964. Arizona's natural environment. ture, Forest Service, Rocky Mountain Forest and Range University of Arizona Press, Tucson. 136p. Experiment Station: 98-102. McClaran, Mitchel P.; Allen, Larry S.; Ruyle, George B. Segura, Gerardo; Snook, Laura C. 1992. Stand dynamics 1992. Livestock production and grazing management and regeneration patterns of a pinyon pine forest in east in the encinal oak woodlands of Arizona. In: Ffolliott, central Mexico. Forest Ecology and Management. 47: P.F.; Gottfried, G.J.; Bennett, D.A.; Hernandez C., V.M.; 175-194. Ortega-Rubio, A.; Hamre, R.H., tech. coords. Ecology Short, Henry L.; Evans, Wain; Boeker, Erwin L. 1977. The and management of oak and associated woodlands: use of natural and modified pinyon pine-juniper wood­ perspectives in the southwestern United States and lands by deer and elk. Journal of Wildlife Management. northern Mexico; 1992 April 27-30; Sierra Vista, AZ. 41: 543-559. Gen. Tech. Rep. RM-218. Fort Collins, CO: U.S. Depart­ Shupe, Howard V.; Solether, Ralph B. 1973. Timber policy ment of Agriculture, Forest Service, Rocky Mountain statement: Coronado National Forest, Southwestern Forest and Range Experiment Station: 57-64. Region. Unpublished Report. Albuquerque, NM: u.s.

McPherson, Guy R. 1992. Ecology of oak woodlands in D(!partment of Agriculture, Forest Servicep Southwest­ Arizona. In: Ffolliott, P.P.; Gottfried, G.J.; Bennett, D.A.; ernRegion.27p.

163 Smith, Norman S.; Anthony, Robert G. 1992. Coues white­ perspectives in the southwestern United States and tailed deer and the oak woodland. In: Ffolliott, P.F.; northern Mexico; 1992 April 27-30; Sierra Vista, AZ. Gottfried, G.J.; Bennett, D.A.; Hernandez C., VM.; Gen. Tech. Rep. RM-218. Fort Collins, CO: U.S. Depart­ Ortega-Rubio, A.; Hamre, R.H., tech. coords. Ecology ment of Agriculture, Forest Service, Rocky Mountain and management of oak and associated woodlands: Forest and Range Experiment Station: 174-176. perspectives in the southwestern United States and USDA Forest Service. 1987. Forest and woodland habitat northern Mexico; 1992 April 27-30; Sierra Vista, AZ. types (plant associations) of Arizona south of the Mo­ Gen. Tech. Rep. RM-218. Fort Collins, CO: U.s. Depart­ gollon Rim and southwestern New Mexico. ment of Agriculture, Forest Service, Rocky Mountain Albuquerque, NM: u.s. Department of Agriculture, Forest and Range Experiment Station: SO-56. Forest Service, Southwestern Region. Stromberg, Julie C.; Patten, Duncan T. 1991. Dynamics of the Van Devender, Thomas R.; Spaulding, W. Geoffrey. 1979. spruce-fir forests on the Pinaleno Mountains, Graham Development of vegetation and climate in the south­ Co., Arizona. The Southwestem Naturalist. 36: 37-48. western United States. Science. 204: 701-710. Touchan, Ramzi; Bennett, Duane A.; Ffolliott, Peter F. 1992. Whittaker, R. H.; Niering, W. A. 1965. Vegetation of the Coppice thinning of Emory oak sprouts: effects on Santa Catalina Mountains, Arizona: a gradient analysis growth, yield, and harvesting cycles. In: Ffolliott, P.F.; of the south slope . Ecology.46: 429-452. Gottfried, G.].; Bennett, D.A.; Hernandez C., VM.; Wilson, Eldred D. 1962. A Resume of the Geology of Ari­ Ortega-Rubio, A.; Hamre, R.H., tech. coords. Ecology zona. Arizona Bureau of Mines Bull. 171, University of and management of oak and associated woodlands: Arizona Press, Tucson .140 p.

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